Bohemian Knotweed

CONTAIN

Origin: Hybrid offspring of Japanese and Giant Knotweed. Much of what is called Japanese knotweed in North America is believed to be Bohemian Knotweed.

Growth Form/Reproduction: Perennial from creeping rhizomes and seeds.

Legal Status: None.

Impacts:Agricultural: Knotweeds can be consumed by grazing animals.Ecological: Considered more aggressive and better adapted to a wider range of habitats than either parent. Dense stands of Bohemian knotweed can compete with other plants and replace native vegetation.Human: Ornamental landscape plants.

Habitat: Prefers open sunny sites. Occupies diverse habitats and tolerates both moist and dry sites, on soils of silt, loams or sands. Spreads most aggressively on moist disturbed sites such as ditches, stream banks and beaches.

Status and Distribution: Widespread in Cowichan Valley, common in Comox Valley, limited in Alberni-Clayoquot, Strathcona, Mount Waddington and Nanaimo. Most common in the CDFmm and CWHmm, present in the CHWvm, CWHvh and CWHdm.

Management Strategy: Once established, Bohemian knotweed is extremely difficult to control; the rhizomes extend meters beyond the clones and tiny fragments are able to regenerate. Digging or hand-pulling results in re-sprouting. Cutting, mowing, grazing and foliar herbicides can reduce top growth but repeated treatments are required for long-term control. A biocontrol program is under development but no biocontrol agents are presently available.